1. Field of the Invention
The present invention relates in general to installation of a pressure sensor and spark plug on a cylinder head of an internal combustion engine and more particularly to a device for temporarily holding a pressure sensor in place within a spark plug attaching hole of a cylinder head prior to installation of a spark plug.
2. Description of the Prior Art
In some automotive engine, a ring-shaped pressure sensor is installed between a spark plug and a cylinder head for measuring a pressure within an engine cylinder and thereby detecting a combustion condition of the engine as disclosed in Japanese Utility Model Provisional Publication No. 62-65529. The pressure sensor includes a piezoelectric ceramic element for converting a cylinder pressure into an electric signal and a lead wire for taking out the electric signal to the outside.
In installation, the pressure sensor is placed in the spark plug attaching hole together with a gasket and firmly held between the spark plug and the cylinder head when the spark plug is screwed into a threaded section of the spark plug attaching hole and tightened by means of a tool such as an impact wrench.
A disadvantage of the prior art installation of the pressure sensor is that the pressure sensor is movable in the spark plug attaching hole prior to installation of the spark plug. Due to this, the pressure sensor is liable to be positioned out of place prior to installation of the spark plug or in the case of the spark plug attaching hole being shallow, there is a possibility that the gasket is dropped off from the spark plug attaching hole prior to installation of the spark plug.
Further, in the case where the pressure sensor is positioned out of place to cause its lead wire, which is soft and easily deformable, to be positioned outside the lead wire receiving groove, such a lead wire may become an obstacle to installation of the spark plug.
For the above disadvantages, it has been difficult to attain automatic installation of the pressure sensor, gasket and spark plug on the cylinder head.